(a) Field of Art
This invention relates to a light fixture which is adapted to accommodate either tungsten filament and gas discharge light bulbs in an adjustable carriage to permit an operator to adjust the focus of the light and to switch bulbs to illuminate a scene, such as the scene of a motion picture film, with different lighting effects.
(b) Prior Art
It is known in the prior art to use both tungsten filament and gas discharge lights to illuminate large areas with either spot or flood lighting. It is also known that tungsten filament bulbs and gas discharge bulbs emit light of different temperature which create different lighting effects. It is within the ordinary skill of a person who constructs light fixtures to make a socket to receive and power both a tungsten filament bulb or a gas discharge bulb.
It is known that light fixtures may be constructed to permit a light bulb to move with respect to a parabolic light reflector to adjust the focus of the light. In this manner one may adjust between spot and flood lighting. One way of focussing a light has a carriage that supports a socket and a bulb to move a bulb linearly with respect to the reflector. This type of mechanism has been used with either gas discharge and tungsten filament light bulbs, but no one such mechanism has been developed for use with both types of bulbs.
Instead, the common practice is that tungsten filament lights are mounted in one type of fixture and gas discharge bulbs are mounted in a different type of fixture and the fixtures are interchanged from time to time while illuminating a scene as is appropriate to the lighting requirement. Specific fixtures have been developed for tungsten filament and gas discharge bulbs, in part, because the source of the light in a tungsten filament bulb is at a different linear position than it would be found in a gas discharge bulb; thus each type of bulb has a different longitudinal range of focus with respect to a reflector in a fixture. Consequently, an operator would have difficulty controlling a servo mechanism to change from spot to flood lighting as bulbs were changed, because the carriage would have to be controlled within different ranges.
The capital cost of having special light fixtures for each type of light bulb may be reduced with the present invention.